The specific goal is to develop and test a Context-Sensitive Ecological Momentary Assessment (CSEMA) system for measuring specific types and total physical activity (PA) in free-living populations. CS-EMA consists of a hand-held computer (personal digital assistant [PDA]) connected wirelessly to a heart rate (HR) monitor and carried/worn on the person being monitored. It collects EMA PA diary information (PA types [e.g., stair climbing], occurrences, duration, self-perceived intensity). The HR monitor continuously transmits data to the PDA where it is stored and analyzed to estimate PA intensity. A time period of moderate or greater intensity (MOD+) PA triggers a CS-EMA prompt (PDA beep) for the subject to enter PA diary data about the period. Following 6-month development, CS-EMA will be evaluated in 2 occupational groups (housekeepers and materials handlers) who perform work tasks that mimic the PA performed by people in their homes, a subject of interest to the PA research community. During project months 7-18, 50 hospital employees (25 housekeepers and 25 materials handlers) will carry/wear the CS-EMA PDA, HR monitor and five 2-axis accelerometers for 1 week (Monday-Friday) during their working hours. During the first 4 days they will use the CS-EMA prompting system to record PA diary information on 2 consecutive days and a paper-and-pencil diary that collects the same information for another 2 consecutive days. The order of use will be random. During all four days they will be monitored by a trained observer who will record their PA. On the fifth day of the week (Friday), the subject will not record PA nor will they be observed. They will only be monitored by HR and accelerometers to evaluate reactivity. The validity analyses during Months 19-24 will compare CS-EMA and paper diary-recording methods against the gold standards of the observer (for PA types, number of bouts, and duration) and the HR for intensity. The subjects will also be assessed regarding their satisfaction with the two measurement methods, their adherence to the reporting protocol and their reactivity to both the observer and the measurement methods. In Months 19-24 we will develop a second generation CS-EMA, by using data gathered during the 12-month study to create algorithms for improving MOD+ PA recognition and for recognizing specific PAs (e.g., climbing stairs). These algorithms will be incorporated into the CS-EMA system and will be used to trigger prompts for subject PA data collection. [unreadable] [unreadable]